Useful candidates for thin film semiconductor and conductor layers for thin-film transistor (TFT) applications include indium gallium zinc oxide (IGZO).
IGZO is used in the TFT backplane of flat-panel displays and monitors. IGZO has higher electron mobility than amorphous silicon and can provide large, high resolution displays with reduced energy requirements.
Significant drawbacks in the production of thin film transistors using these materials are slow manufacturing process speed and throughput, as well as non-uniformity of the composition of deposited layers. These drawbacks are mainly due to the vacuum deposition methods used in the conventional production of thin film transistors.
For example, large scale manufacturing of TFTs, transparent thin-film transistors (TTFTs) and related thin film devices using conventional vacuum-based processes can be unpredictable because of the difficulty in controlling numerous chemical and physical parameters involved in forming a semiconductor or conductor layer of suitable quality on a substrate, both reproducibly and in high yield.
Attempts to increase the efficiency and speed of manufacturing TFT/TTFT materials include use of liquid deposition/printing methods in which particles or precursors for the materials are deposited from an ink. However, ink compositions using components made by sol-gel processes, or that contain nanoparticles, can have drawbacks because they lack stability and compositional uniformity. Their instability is due to the formation of aggregates, particulates or precipitates that cause clogging, blocking or constriction of printing equipment.
Another drawback in the production of thin film transistors is the inability to control the stoichiometry of the product materials. With existing methods and approaches, many useful material compositions are difficult to make because of the lack of control of the stoichiometry. A significant problem is the need to create thin films of semiconducting and conducting materials with controlled compositional homogeneity, uniformity and purity.
There is a long-standing need for solution-based processes for making semiconducting and conducting materials having a predetermined stoichiometry for thin film applications.
There is a need for stable ink compositions having molecular precursor compounds that are completely soluble so that the ink can be used in a high speed and high yield printing process for making semiconducting and conducting materials for thin film transistors.
What is needed are compounds and compositions to produce semiconducting and conducting materials from solution-based processes for thin film transistors, display devices and other products.